1. Field of the Invention
The present invention relates to an induction system for an internal combustion engine, particularly of the kind having a fluid recirculation passage such as a blow-by gas recirculation passage, exhaust gas recirculation passage or the like.
2. Description of the Prior Art
An example of a prior art induction system having a blow-by gas recirculation passage is shown in FIGS. 3 and 4.
Referring to the figures, indicated by the reference numeral 1 is an intake manifold consisting of a collector portion 2 consecutive with a throttle chamber 8 and a branch passage portion 3 consecutive with the downstream end of the collector portion 2 for supplying air to intake ports in a cylinder head 9. The collector portion 2 is formed with a blow-by gas passage 4 integral with the inner wall 2a thereof and having an open end adjacent the throttle chamber 8 so that blow-by gases are mixed with air uniformly. Indicated by the reference numeral 6 is a hose for introducing blow-by gases to the blow-by gas passage 4.
A disadvantage of the prior art induction system is that such a blow-by gas passage is difficult in manufacture and costly. This is particularly true when the blow-by gas passage is so shaped as to have a plurality of outlets for uniformly distributing blow-by gases to each branch passages 3a-3f of the branch passage portion 3 whether it is produced by casting or machining.